This invention relates to a color system and, in particular, is directed to a color system wherein color purity is identified numerically as a percentage of admixtures of colors and is independent of human observations or subjective judgments.
The visible light spectrum is a small part of the electro-magnetic spectrum. The visible spectrum has a wavelength range of about 400 to 700 nanometers. When passed through a prism, white light is dispersed into a continuum of colors. Three of these are considered primary colors. The term "primary color" is used to identify hues which cannot be created by mixtures of any other colors. The additive primary colors are blueviolet, green, and red. (Blueviolet is mistakenly termed "blue" in much of the literature, and most often is hyphenated.)
Light is a physical phenomenon. Those things relating to matter involve chemical phenomena. Depending upon its chemical make-up, matter has the ability to absorb, reflect and/or transmit visible light. When all the components of visible light are absorbed by matter, the object is said to be black. That is, none of the primary components of white light theoretically are either reflected or transmitted by a black object. On the other hand, if all the components of visible light are reflected or transmitted by the object, the object is considered white or clear respectively. When the components of light are absorbed or transmitted in different proportions by an object, color occurs. The color of an object is apparent only when light strikes the object. The object in light has the property of color regardless of it being perceived.
Similarly, for color to be perceived, the viewer must have blueviolet, green, and red receptors. The early work of Newton and others involved with color was postulated on this basis and was later proven by tests conducted by Maxwell and others. The study of color, however, evolved first as an art form and then as a science. Artists and others involved in the use of color decided empirically but incorrectly upon the primary colors and their relationships. They devised a workable system, based on yellow, red, and blue being primary, and therefore assumed it to be valid.
In a publication entitled "Color Compass", published by M. Grumbacher, Inc. of New York, N.Y., there is described a color identification system that employs a wheel, wherein the traditional yellow, red and blue are used as primary pigment or dye colors. These presumed primary colors are situated upon a wheel or disk at 120 degree intervals, and secondary and tertiary colors are situated along the wheel or circle between the primary colors. Unfortunately, this system is based on the erroneous assumption that yellow, red and blue are subtractive primary pigments or colors. This erroneous assumption is a widely accepted method of relating and applying colors. However, because the color wheel is based on a misconception of what constitute true primary colors, its use in a practical sense is limited, and oftentimes produces undesirable results.
At about the turn of the last century, Albert H. Munsell arranged colors in a circle, or wheel, and then arranged them in a spherical form. He experimented with various color charts and perfected the Munsell disk as a means for matching and coordinating colors. Later the Munsell Color Company was formed which still carries on his work based on the Munsell system. Although the Munsell system is quite ingenious, it erroneously considers lightness as a component of color, rather than as an independent variable. This, of course, introduces a great deal of subjectivity into the system and again renders it non-usable as an objective means for identifying and/or using color.
In the early decades of this century, the Colorimetry Committee of the Optical Society of America defined color as a sensation produced by the eye, and therefore a purely subjective concept. Later the committee announced that it had adopted a psychophysiological concept that a subjective human response was a necessary part of color per se and its evaluation.
In 1931, the Commission Internationale d'Eclairage (CIE defined the requirements for specific color in terms of magnitudes of three standard stimuli required to match the average visual color response of a young, normal eye. The tri-stimulus values of the three primary colors that are required to match a given color at each wavelength of an equal energy spectrum are used to identify the primary colors. This produces the familiar "color horseshoe." To avoid negative coefficients, the CIE defined a set of non-physical primaries that permitted each color to be specified by a triplet of non-negative numbers. There has been wide use of triplets to identify colors since that time.